1. Field of the Invention
The present invention relates to path routing of packets with service level guarantees in an optical telecommunication network.
2. Description of the Related Art
Packet networks establish new paths through a given network topology, sometimes termed network tunnel paths (NTPs). New paths are established by implementing a routing algorithm when a packet connection request for the path arrives at the network (an NTP request). The NTP request generally specifies a source, which is the node or router of the network that receives the packets for the connection from an external entity (also termed the “origination” or “ingress” node/router). The NTP request also specifies at least one destination, which is the node or router of the network that ultimately receives the packets for the connection from the source (also termed the “termination” or “egress” node/router). For networks that allow provisioning of guaranteed service levels, sometime called quality of service (QoS) guarantees, the request may also include a requested minimum service level. Service levels commonly provisioned are guaranteed bandwidth for the connection, minimum delay, minimum dropped packets, or guaranteed buffer size. As known in the art, most, if not all, of these service levels may be converted into a quantity called “effective bandwidth” for the routing algorithm.
NTP requests in packet networks following the Internet protocol (IP) may have traffic carried over wavelength division multiplex (WDM) optical networks. Routing of NTP requests occurs through a routing method or algorithm accounting only for packet (i.e., the IP layer) information only. Wavelength routing at the optical devices of the network takes only optical network information (i.e., the optical layer) into account. The typical approach to routing a path of an NTP request is to separate the routing at each protocol or network layer. For example, a routing algorithm may be implemented at the IP layer to route individual requests independently of network provisioning of wavelengths at the optical layer in the WDM optical network to meet overall increases in demand. Wavelength routing of the optical layer sets up a quasi-static logical topology that is then used at the IP layer by the IP routing algorithm.
Many algorithms for routing bandwidth guaranteed paths considering only the IP layer topology and resource information exist in the art, such as widest-shortest path routing, minimum-interference routing, and shortest-path routing with load-dependent weighting. Many algorithms exist in the art for wavelength routing at the optical layer. A key difference between IP layer routing algorithms and wavelength routing algorithms is the characterization of node capabilities. In IP layer routing, the algorithms assume that the node has no switching limitations between links arriving at or leaving the node, and account for link topology and the available/used link capacity when routing a new path through the nodes of the network. However, for wavelength routing, optical network node elements may have different types of wavelength conversion (e.g., optical switching or crossconnect) capabilities, and, thus, these algorithms account for these limitations in wavelength conversion by each node.